FALLS TOWNSHIP, Pa. -- Illinois Sen. Barack Obama didn't wait for the returns from his Mississippi Democratic primary victory yesterday to move on to the next and broader battleground of his protracted struggle with New York Sen. Hillary Rodham Clinton.

Six weeks before the Pennsylvania primary, he came to the state's southeastern corner for a tour and question-and-answer session at a wind turbine plant on the site of U.S. Steel's Fairless Works, once one of the largest steel mills in the world.

Hours later, he would have a chance to celebrate the latest contribution to his delegate lead, which -- while narrow -- has proved a so-far intractable obstacle for the Clinton campaign, whose aides prefer to dwell on her successes in larger states such as Ohio and Texas.

In Mississippi, returns from 25 percent of its precincts showed Mr. Obama gaining 54 percent, to 43 percent for Mrs. Clinton. The Associated Press called the contest in his favor about 8:25 p.m. ET, and CNN did the same about 10 minutes later.

Mr. Obama was winning roughly 90 percent of the black vote, but only about a quarter of the white vote, extending a pattern that carried him to wins in earlier primaries in South Carolina, Alabama, Georgia and Louisiana.

He picked up at least six Mississippi national convention delegates, with 27 more to be awarded. He hoped for a win sizable enough to erase most, if not all, of Mrs. Clinton's 11-delegate gain from last week, when she won three primaries. He had 1,585 delegates to her 1,473. It takes 2,025 to win the nomination.

"Now, we look forward to campaigning in Pennsylvania and around the country," Clinton campaign manager Maggie Williams said in a statement that congratulated Mr. Obama on his victory. Mr. Obama replied, "I'm confident that once we get a nominee, the party is going to be unified."

Mr. Obama used his visit yesterday to the Bucks County plant to highlight proposals to promote green construction and alternative energy sources. The surrounding Bucks County communities are part of the suburban ring around Philadelphia that figures to be one of the most contested battlegrounds in the state's April 22 primary.

A new SurveyUSA poll broadcast on KDKA Television showed the two Democrats virtually tied in the state's southeastern corner, while Mrs. Clinton leads with varying margins elsewhere in the state.

Surrounded by about 200 workers in a semicircle of chairs on the plant floor, Mr. Obama said economic renewal was "not just political rhetoric, it's the cause of my life." He said he had moved back to Chicago after college because he wanted to work at the grass-roots level at a time, in the early '80s, when thousands of steel jobs were leaving Chicago.

Yesterday's meeting with Gamesa Wind Turbines workers offered a low-key contrast to the arena-filling rallies for which his campaign has become known.

"I'll be the president who strengthens our middle class by learning from what happens in places like Fairless Hills," he said."Fairless Hills is doing what Americans have always done. ... You're reclaiming your own future; you're turning Fairless Hills into a center for the green jobs of the future."

His exchanges with the workers lacked the partisan edge that has increasingly dominated his competition with Mrs. Clinton, but their campaigns made sure to provide the minimum daily requirement of acrimony.

In response to remarks that Mrs. Clinton made flaying Mr. Obama's record on energy, the Obama camp responded with a statement claiming that Mrs. Clinton would "say or do anything to win this election."

"Barack Obama isn't about to be lectured on words from someone who's actions spoke much louder when she voted against renewable fuels and higher CAFE [fuel economy] standards until she started running for president, and supported George Bush's disastrous war in Iraq until she started running for president," the statement continued.

The Obama campaign also pressed its rivals to remove Geraldine Ferraro, the 1984 vice presidential candidate, from their finance committee after she was quoted as saying: "If Obama was a white man, he would not be in this position. And if he was a woman [of any color], he would not be in this position. He happens to be very lucky to be who he is. And the country is caught up in the concept."

In a conference call with reporters earlier yesterday, Obama chief strategist David Axelrod called for Ms. Ferraro's ouster, while arguing, "This is part of an insidious pattern that needs to be addressed."

The Associated Press reported that Mrs. Clinton had disavowed Ms. Ferraro's remark. "I do not agree with that," she said. "It is regrettable that any of our supporters, on both sides -- because we've both had that experience -- say things that kind of veer off into the personal. We ought to keep this on the issues."

That wasn't enough for Obama press secretary Bill Burton.

"With Senator Clinton's refusal to denounce or reject Ms. Ferraro," he said in a statement, "she has once again proven that her campaign gets to live by its own rules and its own double standard, and will only decry offensive comments when it's politically advantageous to Senator Clinton."